1. Field of the Invention
The present invention relates to an ink jet recording head and an ink jet recording apparatus for imprinting a plurality of different kinds of ink, such as inks of a plurality of colors, on a recording medium, such as paper.
2. Related Background Art
Among known ink jet recording heads for printing color images, there are so-called integrated multicolor type ink jet recording heads, in which a plurality of heat generating resistance devices (electrothermal conversion devices) matching inks of a plurality of colors and densities are arranged on the same substrate, and nozzles and flow channels matching the respective heat generating resistance devices are also disposed on this substrate (e.g., the Japanese Patent No. 2718939).
In recent years, further improvement in picture quality, especially in terms of the definition and contrast of recorded pictures, has come to be required of color ink jet recording apparatuses. Known ways to meet this requirement include enhancing the definition of pictures by increasing the densities of dye of inks.
However, as the densities of dye of inks are increased, they become more viscous. Increased viscosity entails a slowdown in the refilling of nozzles with inks after they are discharged from the outlet. In short, the higher the densities of dye of inks, the slower the refilling after they are discharged from the outlet.
Therefore, where an ink of a density of dye exceeding a prescribed level of viscosity is used, ink drips may be discharged before the nozzle is fed with a sufficient quantity of ink, which would prevent stable discharging of ink drips.
At the same time, the viscosity of ink varies with the temperature and humidity of the external environment. If, for instance, the temperature or the humidity of the external environment is low, the ink will become more viscous, likely to make stable discharging of ink drips impossible.
Therefore, a color ink jet recording apparatus using inks of densities of dye exceeding a prescribed level of viscosity is more susceptible to inability to stably discharge ink drips when the temperature or the humidity of the external environment is low. Eventually, it may become impossible to normally form main drips of ink, or faulty discharging may occur as a consequence of the deviation of the discharging direction of ink drips from the designed discharging direction or a total failure to discharge ink drips.